Consider the pushdown automation (PDA) P below, which runs on the input alphabet {a, b}, has stack alphabet {$$\bot$$, A}, and has three states {s, p, q}, with s being the start state. A transition from state u to state v, labelled c/X/$$\gamma$$, where c is an input symbol or $$\in $$, X is a stack symbol, and $$\gamma$$ is a string of stack symbols, represents the fact that in state u, the PDA can read c from the input, with X on the top of its stack, pop X from the stack, push in the string $$\gamma$$ on the stack, and go to state v. In the initial configuration, the stack has only the symbol $$\bot$$ in it. The PDA accepts by empty stack.

Which one of the following options correctly describes the language accepted by P?

Consider the following languages:

L₁ = {aⁿ waⁿ | w $$\in$$ {a, b}*}

L₂ = {wxw^R | w, x $$\in$$ {a, b}*, | w | , | x | > 0}

Note that w^R is the reversal of the string w. Which of the following is/are TRUE?

Consider the following languages:

$$\eqalign{ & {L_1} = \{ ww|w \in \{ a,b\} *\} \cr & {L_2} = \{ {a^n}{b^n}{c^m}|m,\,n \ge 0\} \cr & {L_3} = \{ {a^m}{b^n}{c^n}|m,\,n \ge 0\} \cr} $$

Which of the following statements is/are FALSE?

For a string w, we define wR to be the reverse of w. For example, if w = 01101 then wR = 10110.

Which of the following languages is/are context-free?